I need assistance with 7.18 only please...

Exercise 7.18 Repeat Exercise 7.8 for the multicycle ARM processor. Assume the instruction mix of Example 7.5.

7.8 asks "Consider the delays given in Table 7.5. Ben Bitdiddle builds a prefix adder that reduces the ALU delay by 20 ps. If the other element delays stay the same, find the new cycle time of the single-cycle ARM processor and determine how long it takes to execute a benchmark with 100 billion instructions."

Example 7.5 The SPECINT2000 benchmark consists of approximately 25% loads, 10% stores, 13% branches, and 52% data-processing instructions.2 Determine the average CPI for this benchmark.

Solution: The average CPI is the sum over each instruction of the CPI for that instruction multiplied by the fraction of the time that instruction is used. For this benchmark, average CPI=(0.13)(3)+(0.52+0.10)(4)+(0.25)(5)=4.12. This is better than the worst-case CPI of 5, which would be required if all instructions took the same time.